This invention relates to new and useful improvements in tools for testing and adjusting the cams of air brakes on heavy duty vehicles.
It is essential that sufficient clearance be provided and maintained between the cam lever and the actuating valve of the cam in order to prevent the brakes from binding when in the "off" position.
For example it is necessary to maintain approximately 11/2 inches of clearance or movement of the end of the cam lever where same is connected with the actuating rods, in order to ensure the necessary clearance. If more than 11/2 inches is provided, then fill power may not be applied to the brakes and, as mentioned previously, if no clearance is provided there is the danger of the brakes binding even although they are not being actuated.
Due to the inaccessibility of such cam levers and the difficulty of rotating same in order to check the clearance, it is normal to use a short rod such as a centre punch engaged within one of the clevis attaching holes in the end of the lever and attempt to move the lever in an arc in order to test for the clearance. Such a device often slips, because of the pressure required, causing injury to the knuckles of the operator so that it is common practice to tighten the cam up as far as possible and then back off the adjusting nut approximately one-half a turn. This of course is not an accurate way to set clearance and the danger always exists that such brakes will bind even though they are not being used.